Cord for rubber reinforcement, process for producing the same, and rubber product made with the same

ABSTRACT

A reinforcing cord for rubber reinforcement of the present invention includes a reinforcing fiber and a coating film formed on the reinforcing fiber. The coating film is a film formed by drying a coating liquid containing a rubber latex and a vulcanizing auxiliary, and the coating liquid includes a medium that contains at least 50 weight % of water. This reinforcing cord for rubber reinforcement exhibits high adhesiveness to a matrix rubber containing, as its main component, a mixed rubber of a hydrogenated nitrile rubber containing zinc dimethacrylate dispersed therein and a hydrogenated nitrile rubber and therefore can be manufactured easily.

TECHNICAL FIELD

The present invention relates to a reinforcing cord for rubberreinforcement to be buried in a rubber product as a reinforcing materialand to a method of manufacturing the same. The present invention alsorelates to a rubber product reinforced with a reinforcing cord forrubber reinforcement.

BACKGROUND ART

In order to improve the strength and durability of rubber products suchas rubber belts and rubber tires, it generally has been practiced tobury glass fibers, synthetic fibers, etc. in a matrix rubber asreinforcing fibers. Generally, however, the reinforcing fibersthemselves have low adhesiveness to rubber. Accordingly, when thereinforcing fibers are buried in rubber without being subjected tosurface processing, the following problems tend to be caused. That is,the reinforcing fibers and the rubber do not adhere to each other, orthey adhere to each other but the adhesion to each other is not firm,which results in easy exfoliation while in use. Hence, in order toimprove the adhesion of the reinforcing fibers to a matrix rubber and toprevent the quality of the reinforcing fibers from deteriorating,various coating films are formed on the reinforcing fibers. Suchreinforcing fibers have been proposed conventionally(JP63(1988)-270877A, JP6(1994)-306211A, JP7(1995)-138831A,JP7(1995)-179621A, JP10(1998)-238596A, JP11(1999)-158744A,JP11(1999)-217739A, JP11(1999)-240308A, JP11(1999)-241275A,JP11(1999)-241276A, JP2002-309484A, and JP2003-221785A).

JP63(1988)-270877A describes a method of forming a coating film byapplying a mixed processing agent of a condensate of resorcinol andformalin and a hydrogenated nitrile rubber latex (an H-NBR latex) to aglass fiber (a reinforcing fiber), and then drying and curing it. Thisreference describes that glass fiber cords manufactured by this methodhave high adhesiveness to a matrix rubber containing H-NBR as its maincomponent.

With respect to a coating film to be formed on reinforcing fibers, it isnecessary to change/adjust components to be contained therein and itsinternal structure according to the type and characteristics of thematrix rubber. This is because it depends on the type of the matrixrubber whether the coating film has high adhesiveness thereto. Hence,even if the glass fiber cords described in the above-mentioned referenceare useful in the matrix rubber containing H-NBR as its main component,they do not always exhibit high adhesiveness to other types of matrixrubbers.

A rubber composition has been known that contains, as its maincomponents, a hydrogenated nitrile rubber including zinc dimethacrylatedispersed therein (hereinafter also referred to as “H-NBR/ZDMA”) and ahydrogenated nitrile rubber (hereinafter also referred to as “H-NBR”).Since rubber products formed using a matrix rubber containing H-NBR andH-NBR/ZDMA as its main components are excellent in heat resistance, theyare suitable for uses such as timing belts of vehicle engines, etc. Areinforcing cord for rubber reinforcement that exhibits highadhesiveness to the above-mentioned matrix rubber has been proposed inJP11(1999)-241275A. This reinforcing cord for rubber reinforcementincludes a reinforcing fiber as well as a first coating layer and asecond coating layer that are formed sequentially on the reinforcingfiber. The first coating layer is formed with a processing agent thatcontains a condensate of resorcinol and formalin and a rubber latex. Thesecond coating layer is formed with a processing agent that contains arubber compound, a vulcanizing agent, and a maleimide vulcanizingauxiliary as its main components.

This reinforcing cord for rubber reinforcement, however, has problems inthat the process of forming the coating layers is complicated due to thetwo-layer structure that is employed for the coating layers to be formedon the reinforcing fiber and the manufacturing cost is high.Furthermore, since this reinforcing cord for rubber reinforcement ismanufactured using the condensate of resorcinol and formalin and aqueousammonia in forming the first coating layer and an organic solvent suchas toluene in forming the second coating layer, a severe burden isimposed on the environment and especially it is indispensable to takemeasures to provide safe environments for workers.

DISCLOSURE OF THE INVENTION

The present invention was made with attention being given to theproblems as described above. The present invention is intended toprovide a reinforcing cord for rubber reinforcement that exhibits highadhesiveness to a matrix rubber containing H-NBR and H-NBR/ZDMA as itsmain components and that can be manufactured readily, and a method ofmanufacturing the same. Furthermore, another object of the presentinvention is to provide a rubber product in which a reinforcing cord forrubber reinforcement of the present invention is used.

In order to achieve the above-mentioned objects, a method ofmanufacturing a reinforcing cord for rubber reinforcement of the presentinvention includes: (i) applying a coating liquid containing a rubberlatex and a vulcanizing auxiliary onto a reinforcing fiber; and (ii)drying the coating liquid to form a coating film on the reinforcingfiber, wherein the coating liquid includes a medium that contains atleast 50 weight % of water.

A reinforcing cord for rubber reinforcement of the present inventionincludes a reinforcing fiber and a coating film formed on thereinforcing fiber, wherein the coating film is a film formed by drying acoating liquid containing a rubber latex and a vulcanizing auxiliary,and the coating liquid includes a medium that contains at least 50weight % of water.

A rubber product of the present invention includes a matrix rubber and areinforcing cord for rubber reinforcement buried in the matrix rubber,wherein the matrix rubber includes, as its main component, a mixedrubber of a hydrogenated nitrile rubber containing zinc dimethacrylateand a hydrogenated nitrile rubber, and the reinforcing cord for rubberreinforcement is a reinforcing cord for rubber reinforcement of thepresent invention.

Since an aqueous medium is used in forming the reinforcing cord forrubber reinforcement and in the method of manufacturing the same, theenvironment is not affected much and the working environment in whichthe process of forming the coating film is carried out can be improved.Moreover, according to the present invention, the adhesiveness to amatrix rubber that has high resistances to bending fatigue and hightemperature can be improved dramatically through a simple process.Particularly, in the present invention, the coating film can be formedthrough a single coating process using an aqueous medium. In addition,the present invention allows rubber products that are required to havehigher orders of heat resistance and bending fatigue resistance, such astiming belts, to be obtained readily at low cost.

BEST MODE FOR CARRYING OUT THE INVENTION

Embodiments of the present invention are described below.

Embodiment 1

In Embodiment 1, the description is directed to the reinforcing cord forrubber reinforcement of the present invention and the method ofmanufacturing the same. In the method of the present invention, acoating liquid (an aqueous adhesive) containing a rubber latex and avulcanizing auxiliary is applied onto a reinforcing fiber. This coatingliquid includes a medium (a liquid component) containing at least 50weight % of water. The coating liquid then is dried and cured. Thus acoating film is formed on the reinforcing fiber.

The reinforcing fiber to be used in the present invention is notparticularly limited in type and shape as long as it can be buried in amatrix rubber to improve the shape stability and strength of the matrixrubber. Examples of the reinforcing fiber to be used herein includeglass fibers, polyvinyl alcohol fibers that are typified by vinylonfibers, polyester fibers, polyamide fibers such as nylon and aramid(aromatic polyamide) fibers, carbon fibers, polyparaphenylenebenzoxazole fibers, etc. Among them, the glass fibers that are excellentin heat resistance and tensile strength are used suitably.

The type of the glass fibers is not particularly limited. However, ahigh strength glass that is excellent in tensile strength is preferredto a common no-alkali glass due to its suitability for the intended useas reinforcing fibers. With respect to the filament that is the minimumelement of a glass fiber, a common filament having a mean diameter of 5to 13 μm is preferable. Preferably, the glass fiber has a core-sheathstructure that is composed of a core fiber and three to eight peripheralfibers arranged around the core fiber. For instance, 800 to 2000filaments bundled without being twisted can be used for the core fiber.On the other hand, bundles of 200 to 800 filaments twisted in the samedirection can be used for the peripheral fibers. In such a core-sheathstructure, the core fiber serves to effectively improve tensile strengthof the reinforcing fiber while the peripheral fibers serve toeffectively improve bending fatigue resistance of the reinforcing fiber.Accordingly, the reinforcing fiber having this core-sheath structure issuitable for the intended use such as timing belts, etc.

The shape of the reinforcing fiber is not particularly limited as longas it can be buried in a matrix rubber. For instance, the reinforcingfiber to be employed herein can be a staple or a filament or can be of acord, rope, or canvas shape.

An aqueous vulcanizing auxiliary can be used as the vulcanizingauxiliary to be contained in the coating liquid. For instance, aqueousdispersions can be used that include quinone dioximes such asp-quinonedioxime, methacrylates such as lauryl methacrylate and methylmethacrylate, allyls such as DAF, DAP, TAC, and TAIC, maleimides such asbismaleimide, phenyl maleimide, and N,N-m-phenylene dimaleimide, sulfur,etc. Such a vulcanizing auxiliary contained in the coating liquid canimprove the adhesion between the reinforcing fiber and the matrixrubber. Among others, the maleimide vulcanizing auxiliary is preferablesince it specifically improves the adhesion between the reinforcingfiber and the matrix rubber.

The rubber latex to be contained in the coating liquid can be, forinstance, a butadiene-styrene copolymer latex, a dicarboxylatedbutadiene-styrene copolymer latex, a vinylpyridine-butadiene-styreneterpolymer latex, a chloroprene latex, a butadiene rubber latex, achlorosulfonated polyethylene latex, an acrylonitrile-butadienecopolymer latex, an H-NBR latex, etc. Among them, the H-NBR latex canfit best in the matrix rubber to be described in Embodiment 2 andtherefore can improve the adhesion between the reinforcing fiber and thematrix rubber effectively. The rubber latex also can be a blend of someof the above-mentioned latex. The aqueous medium to be described latercan be used for the dispersion medium of the rubber latex, for instance.

The main components of the coating liquid are a rubber latex and avulcanizing auxiliary. In this context, the “main components” denotecomponents whose contents by percentage account for at least 50 weight %of the components (wherein liquids such as the solvent and dispersionmedium are excluded from the components). That is, the total content bypercentage of solid contents of the rubber latex and vulcanizingauxiliary is at least 50 weight % of the solid content of the coatingliquid. Since the physical properties of a composition depend oncontents by percentage of its components, its main componentssubstantially determine the physical properties thereof. Accordingly,when the total content by percentage of the rubber latex and thevulcanizing auxiliary is at least 50 weight % of the coating film, thecharacteristics of the rubber latex and vulcanizing auxiliary dominate.

The medium of the coating liquid is an aqueous medium containing waterwhose content by percentage is at least 50 weight %. An aqueous mediumhas an excellent handling property, allows the concentrations of theabove-mentioned components to be controlled easily, and reduces a burdenon the environment markedly as compared to an organic medium.

The aqueous medium to be used herein can be water or a mixed medium ofanother medium and water. For instance, water or a mixed medium of waterand lower alcohol can be used as the aqueous medium. In this context,the “lower alcohol” denotes alcohol whose carbon number is three orless, and it can be methyl alcohol, ethyl alcohol, n-propyl alcohol, orisopropyl alcohol. Even if the aqueous medium contains a medium otherthan water, the ratio of water in the aqueous medium is at least 50weight % (preferably at least 80 weight %). Preferably, this aqueousmedium contains no solvents that have harmful effects on theenvironment, such as formalin and ammonia. The components that arecontained in the aqueous medium but do not remain after the formation ofa coating film are not considered as components of the coating film. Forexample, in the case of a coating liquid including an aqueous mediumcontaining lower alcohol, the lower alcohol is removed from the coatingfilm substantially completely through heating that is carried out informing the coating film. The lower alcohol contained in the aqueousmedium therefore is not a component of the coating film.

Furthermore, carbon black may be blended into the coating liquid, as acomponent of the coating film. The addition of carbon black allows thecost for manufacturing a reinforcing cord for rubber reinforcement to bereduced and also allows the adhesion between the reinforcing cord forrubber reinforcement and the matrix rubber to be improved effectively.

Moreover, a peroxide may be added to the coating liquid, as a componentof the coating film. The addition of the peroxide allows crosslinkingbetween the coating film and the matrix rubber to be promoted andthereby the adhesion therebetween further improves. The type of theperoxide is not limited. The peroxide to be used herein can be anorganic peroxide such as hydroperoxide, dialkyl peroxide, etc. Theperoxide, however, is required to be one selected from those having areaction velocity comparable with that of the vulcanizing agent that hasbeen blended into the matrix rubber. Among various peroxides, cumenehydroperoxide to be employed in the examples described later is usedsuitably since it is excellent in adhesiveness and handling property.

With respect to the ratio (a weight ratio of solid contents) of thecomponents of the coating film to be formed with the above-mentionedcoating liquid, the ratio of rubber latex/vulcanizing auxiliary(preferably maleimide vulcanizing auxiliary such as bismaleimide)/carbonblack/peroxide is preferably in the range of 100/30 to 70/0 to 50/0 to20 (more preferably 100/30 to 50/10 to 20/5 to 15). Particularly, theratio between the rubber latex and the vulcanizing auxiliary isimportant. An excessively small content of vulcanizing auxiliary resultsin insufficient crosslinking between the coating film and the matrixrubber and exfoliation therefore tends to occur at the interfacetherebetween. On the other hand, an excessively large content ofvulcanizing auxiliary results in a relative reduction in the content ofthe rubber latex. Accordingly, the strength of the coating film itselfdeteriorates, which results in a tendency of insufficient adhesionbetween the reinforcing fiber and the matrix rubber. A preferablecombination of the above-mentioned components is, for instance, acombination of an H-NBR latex, a maleimide vulcanizing auxiliary(particularly bismaleimide), carbon black, and cumen hydroperoxide.

The coating liquid may contain other components such as an inorganicfiller other than carbon black, a plasticizer, an antioxidant, a metaloxide, a crosslinking auxiliary, and a surfactant, as required.

The coating liquid can be prepared by mixing respective raw materialswhile stirring them. The order of addition of the raw materials is notparticularly limited but they generally are put into a blender indecreasing order of amount.

The coating liquid thus prepared is applied to a reinforcing fiber andthen is dried to be cured. Thus a coating film is formed. The method ofapplying and drying the coating liquid is not particularly limited. Inan example of the method, first, a reinforcing fiber is immersed in acoating liquid that has been put in a container and thereby the coatingliquid is applied to the reinforcing fiber. Thereafter, the reinforcingfiber to which the coating liquid has been applied is drawn up from thecontainer and then is passed through a drying furnace and thereby themedium is removed. The drying conditions to be employed for removing themedium are not limited, but for instance, the reinforcing fiber may beexposed to an atmosphere having a temperature of 80° C. to 160° C. for0.1 to 2 minutes.

Thus a reinforcing cord for rubber reinforcement is formed. Preferably,the coating film accounts for a ratio in the range of 10 to 30 weight %(more preferably 12 to 22 weight %) of the reinforcing cord for rubberreinforcement. When this ratio is lower than 10 weight %, it isdifficult to coat the whole surface of the reinforcing fiber with thecoating film. On the other hand, when the ratio exceeds 30 weight %, aproblem tends to occur that the coating liquid drops down in forming thecoating film. In addition, in this case, the coating film is excessivelythick, which tends to cause a problem that, for instance, the centerportion and peripheral portion of the reinforcing fiber have differentcharacteristics from each other. Several reinforcing cords for rubberreinforcement of the present invention may be bundled together to beused.

Embodiment 2

In Embodiment 2, the rubber product of the present invention isdescribed. The rubber product of the present invention includes a matrixrubber (hereinafter also referred to as a “matrix rubber (A)”) and areinforcing cord for rubber reinforcement buried in the matrix rubber(A). The reinforcing cord for rubber reinforcement is the reinforcingcord for rubber reinforcement of the present invention described inEmbodiment 1.

The matrix rubber (A) to be used herein can be a rubber containing, asits main component (50 weight %), a mixed rubber of a hydrogenatednitrile rubber including zinc dimethacrylate dispersed therein(H-NBR/ZDMA) and a hydrogenated nitrile rubber (H-NBR). The mixtureweight ratio of [H-NBR]/[H-NBR/ZDMA] is, for instance, in the range of95/5 to 5/95. The matrix rubber (A) may contain other rubbers as long asit contains the above-mentioned mixed rubber as its main component.Well-known or commercial rubbers can be used for the H-NBR andH-NBR/ZDMA.

The rubber product of the present invention can be obtained by buryingthe reinforcing cord for rubber reinforcement according to Embodiment 1in the matrix rubber (A). The method of burying the reinforcing cord forrubber reinforcement in the matrix rubber is not particularly limited. Awell-known method can be employed without any modifications. The rubberproduct thus obtained has both high heat resistance derived from thecharacteristics of the matrix rubber and high strength and bendingfatigue resistance that are provided by the reinforcing cord for rubberreinforcement buried in the matrix rubber. Accordingly, this rubberproduct is used suitably as a rubber product that is required to haveheat resistance, high strength, and bending resistance, and it isparticularly suitable for timing belts of vehicle engines, etc.

From another aspect, the present invention relates to a method ofmanufacturing a rubber product. This manufacturing method includes themanufacturing method according to Embodiment 1 and a process of buryinga reinforcing cord for rubber reinforcement manufactured by themanufacturing method according to Embodiment 1 in a matrix rubber.

EXAMPLES

Hereinafter, the present invention is described further in detail usingexamples. In the following examples, the dispersion medium of the latexis water.

Example 1

Three glass fibers (that each had an E-glass composition and were formedof 200 glass filaments whose mean diameter was 9 μm) were bundledtogether. A coating liquid whose components are indicated in Table 1below then was applied to the glass fibers. Thereafter, the glass fibersto which the coating liquid had been applied were dried in a dryingfurnace at 150° C. for one minute. Thus, a coating film was formed.TABLE 1 Components Ratio H-NBR Latex (Solid Content: 40 weight %) (*1)100 parts by weight Bismaleimide Water Dispersion  50 parts by weight(Solid Content: 50 weight %)(*1) Zetpol Latex (manufactured by ZEON Corporation)

Subsequently, the glass fibers with the coating film formed thereon weretwisted at a rate of 8 times/10 cm. Thereafter, 11 glass fibers, each ofwhich was formed of the glass fibers twisted as described above, werebundled together and then further were twisted at a rate of 8 times/10cm. Thus a reinforcing cord for rubber reinforcement was obtained. Thecoating film accounted for 20 weight % of the total weight of thereinforcing cord for rubber reinforcement.

Subsequently, evaluations were made with respect to adhesion between theabove-mentioned reinforcing cord for rubber reinforcement and the matrixrubber indicated in Table 2 below. First, a specimen (25 mm (width)×50mm (length)×5 mm (thickness)) having the composition indicated in Table2 was prepared. The reinforcing cord for rubber reinforcement was placedon the specimen in parallel to the long sides of the specimen. This washeated at 170° C. for 30 minutes and thereby the reinforcing cord forrubber reinforcement and the specimen were bonded to each other. Afterthis heat bonding, the specimen was stretched with a tensile tester inthe direction in which the fibers had been arranged, and thereby thepeel strength between the matrix rubber and the reinforcing cord wasmeasured. Furthermore, the fracture surfaces of the specimen wereobserved visually and thereby it was checked whether the fracture was“rubber fracture” in which the whole matrix rubber remained on thereinforcing cord side or “interfacial exfoliation” in which the matrixrubber did not remain on the reinforcing cord side at all. The resultsare indicated in Table 6 below. TABLE 2 Components Ratio H-NBR(*2) 70parts by weight H-NBR/ZDMA(*3) 30 parts by weight ZnO 10 parts by weightStearic Acid  1 part by weight  Carbon Black 30 parts by weight TrioctylTrimellitate  5 parts by weight Sulfur 0.1 part by weight  1,3-bis-(t-butylperoxy-isopropyl)-benzene  6 parts by weight(*2)ZETPOL2020 (manufactured by ZEON Corporation)(*3)ZSC2000L (manufactured by ZEON Corporation)

Example 2

A coating liquid composed of the components indicated in Table 3 belowwas applied instead of the coating liquid used in Example 1. The H-NBRlatex was identical to that used in the coating liquid of Example 1(this also applies to the coating liquids to be described below). Areinforcing cord was produced by the same method as that employed inExample 1 except that the above-mentioned coating liquid was used.Thereafter, its adhesiveness to the matrix rubber was evaluated by thesame method as that employed in Example 1. The results are indicated inTable 6 below. TABLE 3 Components Ratio H-NBR Latex (Solid Content: 40weight %) 100 parts by weight Bismaleimide Water Dispersion  50 parts byweight (Solid Content: 50 weight %) Carbon Black Water Dispersion  20parts by weight (Solid Content: 30 weight %)

Example 3

A reinforcing cord was produced by the same method as that employed inExample 1 except that a coating liquid composed of the componentsindicated in Table 4 below was applied instead of the coating liquidused in Example 1. Thereafter, its adhesiveness to the matrix rubber wasevaluated by the same method as that employed in Example 1. The resultsare indicated in Table 6 below. TABLE 4 Components Ratio H-NBR Latex(Solid Content: 40 weight %) 100 parts by weight Bismaleimide WaterDispersion  50 parts by weight (Solid Content: 50 weight %) Carbon BlackWater Dispersion  20 parts by weight (Solid Content: 30 weight %) CumeneHydroperoxide (Peroxide)  12 parts by weight

Comparative Example 1

A reinforcing cord was produced by the same method as that employed inExample 1 except that a coating liquid composed of the componentsindicated in Table 5 below was applied instead of the coating liquidused in Example 1 and the temperature inside the drying furnace was setat 230° C. Thereafter, its adhesiveness to the matrix rubber wasevaluated by the same method as that employed in Example 1. The resultsare indicated in Table 6 below. TABLE 5 Components Ratio H-NBR Latex(Solid Content: 40 weight %) 65 parts by weight Condensate of Resorcinoland Formalin (Solid 30 parts by weight Content: 8 weight %)(Resorcinol/Formalin = 1/1.3 (mole ratio)) 25% Aqueous Ammonia  1 partsby weight  Water  4 parts by weight

TABLE 6 Compara- tive Example 1 Example 2 Example 3 Example 1 Compo-H-NBR Latex H-NBR Latex H-NBR Latex H-NBR nents BismaleimideBismaleimide Bismaleimide Latex RF of Carbon Black Carbon Black Conden-Aqueous Peroxide sate Adhesive Adhesive 80 N/l0 mm 110 N/10 mm 130 N/10mm 40 N/10 Strength mm Fracture Rubber Rubber Rubber Interfacial TypeFracture Fracture Fracture Exfo- liation

As shown in Table 6, the reinforcing cords for rubber reinforcement ofthe present invention had high adhesiveness to the matrix rubbercontaining the mixed rubber of H-NBR and H-NBR/ZDMA as its maincomponent.

INDUSTRIAL APPLICABILITY

The present invention can be applied to reinforcing cords for rubberreinforcement to be used for reinforcing rubber products and a method ofmanufacturing the same. Furthermore, the present invention can beapplied to various rubber products such as timing belts, various powertransmission belts, heat resistant hoses, etc.

1. A method of manufacturing a reinforcing cord for rubberreinforcement, comprising: (i) applying a coating liquid containing arubber latex and a vulcanizing auxiliary onto a reinforcing fiber; and(ii) drying the coating liquid to form a coating film on the reinforcingfiber, wherein the coating liquid comprises a medium that contains atleast 50 weight % of water.
 2. The method of manufacturing a reinforcingcord for rubber reinforcement according to claim 1, wherein thevulcanizing auxiliary is a maleimide vulcanizing auxiliary.
 3. Themethod of manufacturing a reinforcing cord for rubber reinforcementaccording to claim 1, wherein the rubber latex is a hydrogenated nitrilerubber latex.
 4. The method of manufacturing a reinforcing cord forrubber reinforcement according to claim 1, wherein the coating liquidcomprises carbon black.
 5. The method of manufacturing a reinforcingcord for rubber reinforcement according to claim 1, wherein the coatingliquid comprises a peroxide.
 6. The method of manufacturing areinforcing cord for rubber reinforcement according to claim 1, whereinthe medium is water or a mixed medium of water and lower alcohol.
 7. Areinforcing cord for rubber reinforcement, comprising: a reinforcingfiber; and a coating film formed on the reinforcing fiber, wherein thecoating film is a film formed by drying a coating liquid containing arubber latex and a vulcanizing auxiliary, and the coating liquidcomprises a medium that contains at least 50 weight % of water.
 8. Thereinforcing cord for rubber reinforcement according to claim 7, whereinthe vulcanizing auxiliary is a maleimide vulcanizing auxiliary.
 9. Thereinforcing cord for rubber reinforcement according to claim 7, whereinthe rubber latex is a hydrogenated nitrile rubber latex.
 10. Thereinforcing cord for rubber reinforcement according to claim 7, whereinthe coating liquid comprises carbon black.
 11. The reinforcing cord forrubber reinforcement according to claim 7, wherein the coating liquidcomprises a peroxide.
 12. The reinforcing cord for rubber reinforcementaccording to claim 7, wherein the medium is water or a mixed medium ofwater and lower alcohol.
 13. A rubber product comprising: a matrixrubber; and a reinforcing cord for rubber reinforcement buried in thematrix rubber, wherein the matrix rubber comprises, as its maincomponent, a mixed rubber of a hydrogenated nitrile rubber containingzinc dimethacrylate and a hydrogenated nitrile rubber, and thereinforcing cord for rubber reinforcement is a reinforcing cord forrubber reinforcement according to claim 1.